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Making Bioplastic

·3 mins
Chemistry Bioplastic

I worked in a chemistry lab in 2019, and one of the lab experiments we did involved making bio-plastics. Plastics are polymers, which means they are made out of long chains of molecules. The polymers can be man-made, like nylon (which we also made in the lab), or natural, like DNA.

You could spit into a tube to collect cheek cells and then break the cells to isolate the DNA (which we also did for biology class), and then use the DNA to make plastic, but people will raise their eyebrows if you show them a white slab of bio-plastic and you tell them its is made from your DNA.

A better idea is to use biodegradable polymers from plant sugars to make composite plastics. These are some ingredients you can use:

  • Agar, a polymer made from algae.
  • Cornstarch, a polymer made from corn.
  • Glycerin, a plasticizer made from plant oil or animal fat to make the plastic more flexible.
  • Potato starch, a polymer made from potatoes.
  • Rice starch, a polymer made from rice.
  • Water, a plasticizer that makes the polymers flexible for mixing, and harder once dried.

With those ingredients, you can try mixing different parts of cornstarch, agar, rice starch, potato starch, water, and glycerin. For example, you could start with 10mL of cornstarch, agar, and glycerin, and 50mL of water. Technically, only water and one type of starch is needed.

Then you can mix the ingredients thoroughly and microwave them. I suggest microwaving the mixture for less than 30 seconds at a time and letting the mixture cool down before reheating it, otherwise the mixture will heat up unevenly and the result will look like what it is – dried up potato soup.

The image below shows that the samples in batch 6 heated up unevenly, so the samples had craters because the centers boiled. In the other side, the samples in batch 5 heated up evenly and resembled actual plastic.

Plastics batches

It is kind of autistic, but I had fun making an alien face with food colorant.

I could have also used red food colorant to make an angry red orb monster.

Alien face

Trimmed Alien face

I wanted to test how long the bioplastic would last, so I kept it in a cool, dark place unreachable by sunlight (my room, lol) inside a box along with other college mementos.

It has been more than 5 years, and the alien face did not decompose, but it did shrivel up and become unrecognizable.

Alien face 6 years later

Honestly, it looked the same 3 years ago as it does now. It does not have a weird smell. The texture feels smooth and slightly oily, but not grossly so. I only feel like washing my hands if I think too much about how long it has been sitting around.

I feel conflicted because bio-plastics are supposed to be bio-degradable, but this sample has lasted too long. No roaches, ants, bugs, bacteria, etc., ate it or decomposed it. Hopefully it would decompose naturally in a landfill if it got exposed to rain water, but I am not sure it would be a fast process.

In general, bio-plastics are probably not mass produced because they are more expensive than plastics made from natural gas byproducts or petroleum, but the ingredients are simple, so it is fun working with them.